The present invention relates to protecting porous surfaces from UV degradation. More particularly it relates to novel polymeric compounds useful for this purpose, to intermediates used in their preparation and to methods of applying compositions containing the polymers to porous substrates.
Ultraviolet radiation-absorbing compounds are almost universally present in polymers used in out-door applications. Typically they are molecules of medium molecular weight with specific UV-absorbing moieties, such as benzotriazoles, and are incorporated into the bulk of thermoplastics or rubbers during compounding, extrusion or molding steps. Often they are combined with radical-scavenging molecules, like hindered mines (HALS - hindered amine light stabilizers) or phenols.
UV absorbers can also be formulated into polymer coating systems in order to protect a substrate, but in this case their effectiveness is greatly influenced by the physical nature of the substrate. If the substrate is a hard surface, such as glass, metal or certain finished wood products, conventional UV stabilizers work quite well in protecting the coating in which they are applied and the underlying substrate. On porous substrates however, such as leather, paper or raw wood, their effectiveness is almost entirely lost because most of the active material diffuses below the surface of the substrate.